The primary modes of communication between a service professional for hire and the consumer wishing to hire them has been either by phone, e-mail or text messaging. These methods of communication each have their pros and cons. Phone calls are real-time and allow for immediate clarification on queries but are single-threaded, both the service pro and the consumer can only realistically be on one call at a time.
More importantly, the history of the call is lost unless it was recorded which is not very practical. E-mail has the benefit of providing history but is often used when near-real-time responses are desired. Text-messaging provides near-real-time responses and history but is often tied to a single cell phone/subscriber and doesn't perform well in a business interaction.